The present invention relates generally to power bus systems and, more particularly, to a bus assembly for DC bus links used in motor drive units and the like that can be assembled using a plurality of clamping fasteners. The clamping fasteners are designed to secure the multiple layers of the DC bus together without the need for adhesives.
Often, power delivered from a power source or supply is not properly conditioned for consumption. For example, power plants are linked to power consuming facilities (e.g., buildings, factories, etc.) via utility grids that are designed to be extremely efficient at delivering massive amounts of power. To facilitate efficient distribution, power is delivered over long distances as fixed frequency three-phase alternating current (AC) power. Similarly, in modern vehicle systems, especially hybrid vehicle systems, power management and storage systems handle power in various forms, such as those that are desirable for storage and those that are desirable for consumption. In either case, the power must typically be converted or “conditioned” prior to consumption.
For example, motors and their associated loads are one type of common inductive load employed at many consuming facilities that require power conditioning. When a motor is the consuming point, power “conditioning” systems are utilized to convert the fixed frequency AC power delivered over utility grids to a form suitable for driving the motor. To this end, power conditioning for motor systems typically include AC-to-DC (direct current) rectifiers that convert the utility AC power to DC power applied to positive and negative DC buses (i.e. across a DC link). The power distributed across the DC buses is then converted, for example by use of an inverter, to AC power designed to drive the motor.
Though the above-described system was described with respect to power conditioning for motor systems, such DC bus systems are utilized in a wide range of systems and applications. That is, regardless of the particulars of the consuming components or ultimate application within which the DC bus is employed, DC bus assemblies are often utilized to distribute DC power across various components for reconditioning, storage, and/or consumption.
To create a DC bus assembly, a variety of laminates or adhesively bound components are utilized. For example, a first sheet of copper or similar conductor is arranged as the negative bus line. A second sheet of copper or other conductor is then arranged over the negative bus line and separated by an insulator to serve as the positive bus line. Additional layers that are separated by insulation layers may then be arranged over or between the positive and negative bus layers.
In most applications, the DC bus assembly must be structurally sound so that various components can be securely mounted to the DC bus assembly. That is, each layer in the DC bus assembly must be joined to form a composite structure capable of at least partially supporting components mounted to the assembly. Furthermore, the DC bus assembly must meet various environmental and operational tolerances, such as vibration and heat tolerances. For example, in the above-described example of a motor drive system, typically, the DC bus must have sufficient structural integrity to support both the rectifier and the inverter, as well as various additional components, such as capacitors, water cooling systems, and the like. Furthermore, the DC bus must be able to sustain its structural integrity when subjected to vibrations and high temperatures often associated with motor systems.
To create a DC bus assembly that is suitable for the desired application (i.e. has suitable structural integrity and meets the vibration and temperature constraints), the layers (conductors and insulators) are typically bonded together using adhesives. That is, each conductive layer is bonded to each adjacent insulating layer, such that the assembly is formed by alternating layers of conductor and insulator that are all bonded through adhesives. These laminated DC bus structures provide noise cancellation properties and have become commonplace in power conversion equipment.
While such manufacturing methods have long been employed to great success with meeting the structural requirements needed to withstand vibrations and temperature changes associated with a wide variety of environments, they are rather costly. In particular, the process of aligning and gluing the individual layers requires a high degree of skill because the manufacturer must carefully align the adjacent layers to ensure that adjacent conductors; will not be in contact and will not later move into contact when the separating insulator is subjected to heat and vibration.
As such, the cost of more complex bus structures is often prohibitive. For example, a “3D” bus structure, where the bus sheets are bent to extend into multiple planes, is often cost prohibitive because the process of correctly aligning and gluing adjacent layers simultaneously across multiple planes is extremely difficult, if not impossible. Therefore, though such a 3D bus structure could be advantageously utilized in a wide variety of systems since it would permit the size and shape of the bus to be more compact and/or adapted to fit into non-traditional environments, it is generally foregone in favor of the traditional flat or planar bus design due to cost and quality control constraints.
Therefore, it would be desirable to have a system and method for creating Et power bus assembly that reduces manufacturing costs and complexities, is more adaptable to various bus designs, and provides increased structural integrity.